The present invention relates to a movable assembly used in a cylinder type linear motor that reciprocally moves inside a stator of the cylinder type linear motor.
In conventional cylinder type linear motors, a movable core, considering a path of magnetic flux, employs a laminated structure in which silicon magnetic steel plates are laminated in such a manner that a radial direction of a direct drive shaft, on which the movable core is securely mounted, is a direction of lamination. Such a laminated structure is shown in FIG. 7 of Japanese Patent Disclosure No. 2000-236653. Japanese Patent Disclosure No. 2002-359962 discloses a construction of another cylinder type linear motor that this applicant proposed previously. In the cylinder type linear motor shown in the previous application, an array of permanent magnets is mounted on a square-columnar structured magnet mounting portion of the movable assembly.
The conventional movable core adopts the aforementioned laminated structure to reduce eddy current loss. However, as can be seen in Japanese Patent Disclosure No. 2002-359962, depending on the condition of operation no practical problem may arise even if the steel plate laminated structure is not used in the movable core. In light of a mass production of the movable core, the laminated structure such as shown in FIG. 7 of Japanese Patent Disclosure No. 2000-236653 is costly and not practical because the structure is complex and because two or more kinds of steel plates in different shapes need to be prepared. It is therefore more practical to form a movable core by cutting, as in the case of the movable core of Japanese Patent Disclosure No. 2002-359962. The structure of the latter movable core, however, is not suited to a low-cost production.
An object of this invention is to provide a movable assembly for a cylinder type linear motor which can be manufactured at low cost without requiring a cutting process while keeping its magnetic characteristics from deteriorating.
Another object of this invention is to provide a movable assembly for a cylinder type linear motor which can realize the above objective without increasing the kinds of parts used.
Still another object of this invention is to provide a movable assembly for a cylinder type linear motor whose magnetic characteristics are improved by adopting a rotation prevention structure.
Yet another object of this invention is to provide a movable assembly for a cylinder type linear motor which can be manufactured easily.
A further object of this invention is to provide a movable assembly for a cylinder type linear motor which is not easily damaged.
A further object of this invention is to provide a movable assembly for a cylinder type linear motor which enables the movable core to be formed more compactly.
A further object of this invention is to provide a movable assembly for a cylinder type linear motor which enables the movable core to be reduced in weight.
A further object of this invention is to provide a movable assembly for a cylinder type linear motor which can increase a connecting strength in an axial direction between the movable core and the direct drive shaft.
A further object of this invention is to provide a cylinder type linear motor which is less expensive than conventional motors.